The present invention relates to a road traffic weather-monitoring system which monitors fog rise, snowfall and other weather conditions on the road, analyzes weather conditions based on the observed data, and forecasts dangers in the driving environment, and also relates to a self-luminous road sign system which provides visual guidance and displays information to drivers.
In order to assist the safety of road traffic, a conventional system utilizes an ITV camera as a device for detecting road conditions, and displays a detection output from the ITV camera by means of a controller device having a display part (hereinafter mentioned as Prior Art 1). In this system, a road manager who takes charge of this controller device makes a comprehensive judgement based on the road information displayed on the display part, the road information on other areas, the weather forecast, etc. This judgement is outputted to a certain display device, which provides drivers with the road weather information or indicates safe driving signs. As the examples of conventional self-luminous road installations, use have been made of self-luminous information panels for notifying drivers of road information, LED-equipped vision guidance signs for representing a curved line shape that matches the curve on the road. The luminous part in these self-luminous road installations can be regulated at a fixed brightness, or two-stage brightness control can be applied to adjust the brightness for the day and the night, respectively.
As disclosed in Japanese Patent Application Laid-open No. H9-128688, a system for assisting safe road travel (hereinafter mentioned as Prior Art 2) comprises obstruction detecting means which includes a visibility meter and an obstruction detection radar for detecting the road driving environment, and displaying/warning means which is controlled in accordance with the output from the obstruction detecting means. These means are combined as an obstruction detecting/warning device, which is serially installed along the central reserve or a side of a road.
This system has the displaying/warning means integrated into the obstruction detecting/warning device, which is serially located along the central reserve or a side of a road. The display modes of the displaying/warning means include sound, text display, indication light (in regard to color, brightness and flash interval) and the like, and these modes can be applied singly or in combination.
As mentioned above, Prior Art 1 uses an ITV camera as the device for detecting road conditions. The ITV camera, however, is very expensive and should be mounted on a large gatepost or a giant system. Besides, in order to provide detailed information to drivers, a number of ITV cameras should be installed at required locations. Hence, it is practically impossible to place so many ITV cameras in the above manner. In another respect, since this system depends on a road manager for a comprehensive judgement, the system requires much time for such judgement and fails to give real-time information. What is worse, this self-luminous road installation is controlled to give a light at a fixed brightness. Accordingly, when visibility drops under bad weather conditions (e.g. fog, snow), the luminous brightness is seriously degraded from the viewpoint of drivers. As a consequence, the signing function as the road sign device is impaired. This problem may be solved by setting the luminous brightness of a sign, based on the low visibility situation under poor weather conditions. However, drivers find such illumination too bright in the night and feel awkward even during the day. Thus, this attempt is rather dangerous to the drivers, only to create another problem. Besides, when the level of luminous brightness is intensified, the structure consumes a greater amount of electric power and, therefore, is uneconomical.
As for Prior Art 2, the system does not rely on the centralized management by a road manager, and it assists drivers"" safe driving by furnishing local or fixed individual information. In this case, it is difficult to grasp foggy, snowy or other conditions in a wide area properly, or to assist safe driving in compliance with the changing weather conditions in a particular area or the conditions across some areas. Besides, the displaying/warning means provides a single type of information merely by issuing a warning in response to obstructions on the road. More disappointingly, despite the fact that the visual perceptibility is adversely affected under a low visibility condition, the information is displayed without any consideration.
The present invention has been made for the purpose of solving these problems. The first object is to provide a road traffic weather-monitoring system which properly grasps foggy, snowy and other conditions in a wide area and which allows a road manager and others, in response to such conditions, to issue real-time weather information to drivers, thereby contributing to safe vehicle travel.
The second object is to provide a self-luminous road sign system which prevents degradation of the luminous brightness of a self-luminous road installation and improves its visual perceptibility even in a poor visibility situation, and which ensures reliable visual guidance.
For the purpose of achieving the above object, the structure of the road traffic weather-monitoring system according to the present invention is described with reference to FIG. 1 which is a conceptual block diagram thereof. A road traffic weather-monitoring system of the present invention comprises a plurality of sensor units 1 . . . 1, located in an observation area on a road, for detecting weather conditions in the observation area; and an information processing and management department 2 for centralized management of weather information detected by each of the sensor units 1 . . . 1, in which department analysis of the weather conditions in the observation area is made on the basis of the weather information so as to predict any danger in a driving environment.
This arrangement enables precise understanding of weather conditions (e.g. fog, snow) over a wide area, and contributes as an information source for an automatically operating, extensive road information system. As a result of centralized management of the weather conditions, actual conditions in the area can be grasped as a map, and the acquired data can be also utilized as basic data for investigation of the accident occurrence mechanism, etc.
In this arrangement, the observation area may be sectioned into a plurality of triangles, and each of the sensor units 1 . . . 1 may locate at vertices of each triangle.
This arrangement facilitates identification and prediction of the range of a foggy or snowy area, and also improves the precision of obtained weather conditions.
Preferably, each of the sensor units 1 . . . 1 is at least equipped with a visibility meter and an illuminance meter, and may be equipped with an anemovane and a thermometer as well as the visibility meter and the illuminance meter.
When each of the sensor units 1 . . . 1 are equipped with a visibility meter and an illuminance meter, the visibility meter provides visibility information such as the atmospheric particle concentration and the outdoor brightness in the road environment, while the illuminance meter gives the background brightness on the road. Additionally, the anemovane and the thermometer can furnish more detailed weather information. As a result, it is possible to grasp and predict the degree of fog rise (fog thickness, visible distance) and the snowing conditions (levels of snowing, snowstorm and visibility limitation; visible distance) in a proper and precise manner.
Further, the road traffic weather-monitoring system according to the present invention preferably includes road installations 4 . . . 4 which are connected to network communication means 3 by wire or radio communications, and which output and display, via the communication means, output information processed through the information processing and management department 2.
This arrangement contributes to safe driving by supplying drivers with proper real-time information.
The output information processed through the information processing and management department may be delivered to the Internet 5 by wire or radio communications. In this case, real-time weather information on the road environment can be easily acquired from each of terminals 6 . . . 6 connected to the Internet 5.
In addition, a self-luminous road sign system of the present invention comprises a sensor unit for detecting weather conditions, a self-luminous road installation which includes a sign part equipped with an illuminant, a control part which controls luminous brightness or information display of the sign part based on weather information detected by the sensor unit.
In the present invention, it should be understood that the sign part includes a luminous device for vision guidance (e.g. delineator), a road information panel for displaying text information or the like, and an arrow or other signs, each of which employs an illuminant as the display means.
In this arrangement, the sensor unit is equipped with a visibility meter and an illuminance meter. On the other hand, the control part is arranged to calculate an optimum luminous brightness which provides a predetermined contrast in a driving environment, based on a road background brightness that is previously obtained by the illuminance meter, and to control luminous brightness or information display of the sign part, based on the optimum luminous brightness and depending on visibility information that is outputted from the visibility meter.
This arrangement can provide drivers with information on an area where visibility is limited due to fog, snow, etc., and can advise them to drive carefully in the visibility-limited area, thereby reducing the risk of traffic accidents. Besides, within the area of limited visibility, the self-luminous road installation can notify drivers of the information, which is displayed at a properly controlled luminous brightness and in a readily recognizable display mode or sign mode. This is also contributory to safe driving.
As an additional arrangement, the sign part may be constituted with a vision guidance sign or a self-luminous information panel.
As a further arrangement, the sensor unit and the self-luminous road installation may be integrated as a road installation unit. In this case, it is preferable that the road installation unit controls, by wire or radio communications, luminous brightness or information display of the sign parts in the own road installation unit and one or more other road installations.
Furthermore, the control part may be arranged to control luminous brightness of the sign part in the self-luminous road installation to give a prescribed luminous brightness, by adjusting a pulse duration of a pulse voltage which is applied to the illuminant.